Objective To evaluate retrospectively whether posterior longitudinal ligament(PLL)adhere to dura mater in the patients with cervical spondylotie myelopathy(CSM)or not before the anterior cervical operation.Methods From December 2005 to January 2007,of 18 patients with CSM the adhesion between PLL and dura mater was found in the anterior cervical operation.The patients included of 11 males and 7 females,with mean age of 65.4 years (range 55-72 years).All the patients were measured by CT and MRI before operation.There were 12 cases of dual-segmental cervical intervertebral disc herniation,6 of tri-segmental disc herniation.The former cases were treated with one level corpectomy and titanium mesh or iliac grafting and cervical anterior plate,and the latter with an additional cervical cage in the intervertebralspace.The floatation method was used to deal with the adhesion.The fitness between the two radiological methods was analyzed by matched-pairs Kappa eoemcient test.Results The nerve functions of all the patients were improved after anterior cervieal decompression.The mean score of JOA was increased from 9.6 of pre-operation to 12.1 of post-operation.There were 4 cases with injury in dura mater,which healed after appropriate dealing with the leakage of cerebrospinal fluid.None of lacerated dura was directly repaired during the operation.The condition of the coarse touch and bur between intervertebral disc and dura mater were found in CT transverse scanning.The thickening of the PLL and the unsymmetrical space between inferior and superior subdural cavity was found in MRI.The coefficient test proved that the difference of the CT and MRI was significant in finding the adhesion.Conclusion MRI iS better than CT in finding the adhesion between the PLL and dura mater in CSM before operation,besides the floatation method should be good to deal with the adhesion.